With the rapid development of mobile communications technologies, mobile communications systems in multiple standards have emerged, such as, Global System for Mobile Communications (GSM) networks, General Packet Radio Service (GPRS) networks, Wideband Code Division Multiple Access (WCDMA) networks, CDMA-2000 networks, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) networks, and Worldwide Interoperability for Microwave Access (WiMAX) networks. Besides providing voice communications services, generally, these mobile communications systems further provide data communications services; therefore, a user may use the data communications services provided by these mobile communications systems to upload and download various types of data.
At present, there are two types of methods for uploading and downloading data with a data communications service provided by an existing mobile communications system:
in one aspect, in a method for a single user equipment (UE), even though other enhanced communication means are used to improve reliability and/or a throughput rate of data transmission of the user equipment, for example, coordinated multipoint transmission (CoMP) is used to improve reliability of a user equipment at a cell edge, or carrier aggregation (CA) is used to improve a throughput rate of a user, the method has the disadvantage that, once an environment of the user equipment gets worse, the throughput rate and/or the reliability of data transmission of the user equipment will decrease dramatically;
in another aspect, in a method for two user equipments, to solve the foregoing problem, a concept of synthetic communications is put forward, and in synthetic communications, both uplink and downlink data may be forwarded by other user equipments; communication between the user equipments may be implemented by using short-distance technologies, such as WIFI and Bluetooth, and may also be implemented by using Long Term Evolution D2D (LTE D2D); a manner of uplink multi-user multiple-input multiple-output (MU-MIMO) in an LTE system is virtual multiple-input multiple-output (virtual-MIMO), that is, a base station (BS) schedules two user equipments to send, on same time-frequency resources, data of the two user equipments, so as to implement MIMO transmission; disadvantages of the method are that, it is required that channel orthogonality of the user equipments is good, and received signal-to-noise ratios of the two user equipments at the base station cannot differ significantly; otherwise, a user equipment with a poor channel condition may receive strong interference, and therefore, although virtual-MIMO brings a gain, its application scenarios are limited, and moreover the gain is small.
In conclusion, the user needs an MU-MIMO manner which is based on precoding, has a low receiving condition for a user equipment channel, and has high uplink spectral efficiency.